1999/05/31 by E. B. Ford, Eric B. Ford, Kriten J. Joshi +5 · 4 citations
Earth and Planetary Sciences · Physics and Astronomy · #Astro and Planetary Science #Astronomy #Astrophysics #Binary pulsar #Celestial mechanics #Eccentricity (behavior) #Exoplanet #Geometry #High-pressure geophysics and materials #Millisecond pulsar #Orbital decay #Orbital eccentricity #Orbital elements #Perturbation (astronomy) #Physics #Planet #Planetary mass #Planetary system #Precession #Pulsar #Radial velocity #Satellite #Solar System #Stars #Stellar, planetary, and galactic studies #Triple system #astro-ph
paper · pdf · doi:10.1086/308167
34 pages, including 11 figures, to appear in ApJ, Jan 1, 2000. Revised version, including some significant additions
arxiv created 1999/11/12 · openalex publication_date 2000/01/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present a new theoretical analysis of the PSR B1620-26 triple system in the globular cluster M4, based on the latest radio pulsar timing data, which now include measurements of five time derivatives of the pulse frequency. These data allow us to determine the mass and orbital parameters of the second companion completely (up to the usual unknown orbital inclination angle i 2 ). The current best-fit parameters correspond to a second companion of planetary mass, m 2 sin i 2 ≃ 7 × 10 -3 M ☉ , in an orbit of eccentricity e 2 ≃ 0.45 and semimajor axis a 2 ≃ 60 AU. Using numerical scattering experiments, we study a possible formation scenario for the triple system, which involves a dynamical exchange interaction between the binary pulsar and a primordial star-planet system. The current orbital parameters of the triple are consistent with such a dynamical origin and suggest that the separation of the parent star-planet system was very large, ≳50 AU. We also examine the possible origin of the anomalously high eccentricity of the inner binary pulsar. While this eccentricity could have been induced during the same dynamical interaction that created the triple, we find that it could equally well arise from long-term secular perturbation effects in the triple, combining the general relativistic precession of the inner orbit with the Newtonian gravitational perturbation of the planet. The detection of a planet in this system may be taken as evidence that large numbers of extrasolar planetary systems, not unlike those discovered recently in the solar neighborhood, also exist in old star clusters.